This invention relates generally to material and coating test fixtures and particularly to a fretting corrosion test fixture.
Fretting describes corrosion damage occurring at contact areas between materials under load subjected to small relative movement or slip. The fretting corrosion damage appears as pits or grooves in the metal surrounded by corrosion debris and is also known as friction oxidation, wear oxidation, chafing, and false brinelling. Fretting has been observed at the interface of metallic joints in engine components, automotive parts and airframe structures. Fretting corrosion is very detrimental because of the destruction of metallic components and the formation of oxide and metallic particulate. Frequently, the result is a loss of tolerances and loosening of mating parts. Further, fretting causes fatigue fractures since the loosening of components permits excessive strain, and the pits formed by fretting act as stress-raisers.
The basic requirements for the occurrence of fretting corrosion are:
1. The interface must be under load;
2. Vibration or repeated relative motion between the two surfaces must occur; and
3. The load and the relative motion of the interface must be sufficient to produce slip or deformation on the surfaces.
Methods and fixtures for performing fretting corrosion studies primarily involve lubrication wear equipment. One other method of inducing fretting corrosion wear is to alter fatigue testing equipment by applying normal loads to induce fretting fatigue. Testing in high temperature environments often require complex and relatively expensive test fixtures not readily adaptable for placing test specimens within a high temperature environment.